Methods and apparatus determining and/or using overshoot control of write current for optimized head write control in assembled disk drives

ABSTRACT

The invention includes a testing method which may be applied to at least one writer in a disk drive during the self-test phase to generate write parameters, focused on the Over Shoot Control (OSC) of the write current parameter to improve the reliability of write operations by that writer. The Minimum OSC is used for write operations in normal temperatures. The Optimum OSC is used for a first lower temperature range, preferably between essentially 15° Centigrade and essentially 5° Centigrade. The Maximum OSC is preferred below essentially 5° C. The Minimum OSC should preferably guarantee both an Adjacent Track Write (ATW) criteria, as well as guarantee a Write Induced Instability (WII) criteria. The invention includes the write parameter collection, as well as the disk drive containing the generated write parameter collection. The invention also includes the method of using that write parameter collection to control a writer while writing to tracks belonging to the radial zone collection and program systems implementing the invention&#39;s methods.

This application claims the benefits of Provisional application Ser. No.60/339,367, filed Dec. 13, 2001.

TECHNICAL FIELD

This invention relates to determining optimized head write parameters toimprove hard disk reliability in the manufacturing process, specificallyin the self-test phase of an assembled disk drive.

BACKGROUND ART

Disk drives are an important data storage technology. Read-write headsare one of the crucial components of a disk drive, directlycommunicating with a disk surface containing the data storage medium. Itis crucial that each read-write head function reliably, otherwise thedisk drive using that read-write head will fail to function reliably.This invention is focused on the optimized control of each read-writehead during write operations within the disk drive. Before disclosingthe invention, some relevant prior art will be discussed.

FIG. 1A illustrates a typical prior art high capacity disk drive 10including actuator 30 with voice coil 32, actuator axis 40, actuatorarms 50–58 with head gimbal assembly 60 placed among the disks.

FIG. 1B illustrates a typical prior art high capacity disk drive 10 withactuator 20 including actuator 30 with voice coil 32, actuator axis 40,actuator arms 50–56 and head gimbal assemblies 60–66 with the disksremoved.

FIG. 2A illustrates a head gimbal assembly 60 including head suspensionassembly with head slider 100 containing the read-write head 200 of theprior art.

Since the 1980's, high capacity disk drives 10 have used voice coilactuators 20–66 to position their read-write heads over specific tracks.The heads 200 are mounted on head sliders 100, which float a smalldistance off the disk drive surface 12 when in operation. The flotationprocess is referred to as an air bearing. The air bearing is formed bythe read-write heads 200, illustrated in FIGS. 2A, and slider-headgimbal assembly 60, as illustrated in FIGS. 1A–2A. The flying height ofthe air bearing is very small, often about 100 Angstroms, or about 0.4millionths of an inch.

Often there is one head per head slider for a given disk drive surface.There are usually multiple heads in a single disk drive, but foreconomic reasons, usually only one voice coil actuator.

Voice coil actuators are further composed of a fixed magnet actuator 20interacting with a time varying electromagnetic field induced by voicecoil 32 to provide a lever action via actuator axis 40. The lever actionacts to move actuator arms 50–56, positioning head gimbal assemblies60–66, and their associated head sliders 100 containing read-write heads200, over specific tracks with speed and accuracy. Actuators 30 areoften considered to include voice coil 32, actuator axis 40, actuatorarms 50–56 and head gimbal assemblies 60–66. An actuator 30 may have asfew as a single actuator arm 50. A single actuator arm 52 may connectwith two head gimbal assemblies 62 and 64, each with at least one headslider.

FIG. 2B illustrates the relationship between the principal axis of anactuator arm 50 containing head gimbal assembly 60, which in turncontains head slider 100, as found in the prior art.

FIG. 2C illustrates a simplified schematic of a disk drive controller1000 of the prior art, used to control an assembled disk drive 10.

Disk drive controller 1000 controls an analog read-write interface 220communicating resistivity found in the spin valve within read-write head200.

Analog read-write interface 220 frequently includes a channel interface222 communicating with pre-amplifier 224. Channel interface 222 receivescommands, from embedded disk controller 100, setting at least theread_(—)bias and write_(—)bias.

Various disk drive analog read-write interfaces 220 may employ either aread current bias or a read voltage bias. By way of example, theresistance of the read head is determined by measuring the voltage drop(V_(—)rd) across the read differential signal pair (r+ and r−) basedupon the read bias current setting read_(—)bias, using Ohm's Law.

Today, a disk drive performs an initialization process 1400 includingwhat is often known as read channel optimization. Read channeloptimization is supposed to find the best parameters for read/writeoperations, which include, at least, a read bias current (Ir), writecurrent lw and write boost.

Channel Statistical Measurements (CSM) are a standard system used inassembled disk drives to estimate channel performance, by measuringamplitude. The testing of disk drives by CSM gives only a partialquality measure. A more thorough quality measure is to determine the BitError Rate (BER).

As magnetic recording head 200 becomes smaller in physical size, thereis an increased need optimize write field control in an assembled diskdrive to minimize reliability problems. This need is difficult tofulfill, because it requires first discovering what are the reliabilityproblem mechanisms within the assembled disk drive, and then configuringthe disk drive to minimize the effects of the reliability problemmechanisms.

SUMMARY OF THE INVENTION

The invention addresses at least the needs discussed in the background.

The invention optimizes the write performance of a writer within a diskdrive 10, including a read-write head 200 accessing a rotating disksurface 12, the coupled preamplifier 224, and the channel interface 222coupled to the preamplifier 224 as illustrated in FIG. 3A.

The inventors discovered that the OverShoot Control (OSC) of the writecurrent (Wc) should be controlled based upon the write field strength ofthe specific writer within the disk drive. Different writers within thesame disk drive have been found to possess distinct write fieldstrengths, requiring distinct OSC settings during normal temperatureoperation. The inventors have found that low temperature conditionsagain need distinct OSC settings based upon the write field strength ofthe writer.

These discoveries lead the inventors to the test method aspect of theinvention, which is applied to at least one writer in a disk driveduring the self-test phase of its manufacture. The testing method 2000of FIGS. 3A–3B, generates write parameters 2900 of FIG. 3A, focused onthe Over Shoot Control (OSC) of the write current parameter to improvethe reliability of write operations by that writer. The OSC parameter isinvolved in at least the operation of the preamplifier 224.

The inventors discovered that a writer with a strong write field sufferssignificant reliability loss with high OSC due to increases in AdjacentTrack Write (ATW) errors, Track Per Inch (TPI) margins, Write InducedInstabilities (WII), read-write head degradation, and Head to DiskInterference (HDI) caused by Thermal Pole Tip Protrusion (TPTP). Theinventors also found that a writer with a weak write field does notsuffer significant reliability loss with high OSC, opening the door tousing higher OSC values without the same problems as a strong writer.

The inventors have found that determining at least three separate OSCparameters to be preferred for write operation control of the writer.The Minimum OSC is used for write operations within a normal temperaturerange. The Optimum OSC is preferably used for write operations in afirst lower temperature range, preferably between essentially 15°Centigrade and essentially 5° Centigrade. The Maximum OSC is used forwrite operations below the first lower temperature range.

The Minimum OSC should preferably guarantee both an Adjacent Track Write(ATW) criteria, as well as guarantee Write Induced Instability (WII)criteria.

The inventors have found the test method should preferably be applied toat least four radial zones of the disk surface accessed by the writer,and then preferably interpolated to each radial zone of the disksurface. The radial zones of the disk surface each include multipletracks on that disk surface with radial distances within that radialzone.

The test method should preferably be applied to each writer in the diskdrive.

The invention includes the write parameter collection 2900 illustratedin FIG. 3A and generated by the test method 2000, as illustrated inFIGS. 3A–3B, as well as the disk drive 10 containing the generated writeparameter collection 2900. The invention also includes the method ofusing 2500 write parameter collection 2900 to control a writer222-224-200 while writing to tracks belonging to the radial zonecollection 2910, and the program systems implementing these methods 2000and 2500.

These and other advantages of the present invention will become apparentupon reading the following detailed descriptions and studying thevarious figures of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a typical prior art high capacity disk drive 10including actuator 30 with voice coil 32, actuator axis 40, actuatorarms 50–58 with head gimbal assembly 60 placed among the disks;

FIG. 1B illustrates a typical prior art high capacity disk drive 10 withactuator 20 including actuator 30 with voice coil 32, actuator axis 40,actuator arms 50–56 and head gimbal assemblies 60–66 with the disksremoved;

FIG. 2A illustrates a head gimbal assembly 60 including head suspensionassembly with head slider 100 containing the read-write head 200 of theprior art;

FIG. 2B illustrates the relationship between the principal axis 110 ofan actuator arm 50 containing head gimbal assembly 60, which in turncontains head slider 100, as found in the prior art;

FIG. 2C illustrates a simplified schematic of a disk drive controller1000 of the prior art, used to control an assembled disk drive 10;

FIG. 3A illustrates aspects of the invention as a refinement of FIG. 2C;

FIG. 3B illustrates a detail flowchart of program system 2000 of FIG. 3Agenerating write parameters 2900 including an OverShoot Control (OSC)collection 2920 of FIG. 3A, regarding a writer communicating with themembers of a radial zone collection 2910;

FIG. 3C illustrates a detail flowchart of operation 2012 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection 2910 members, optimizing the OSC Collection 2920 members tocreate the BER;

FIG. 4 illustrates the effects of the Write Strength 2902 of variouswriters with and without the presence of Thermal Pole Tip Protrusion(TPTP), with the Bit Error Rate (BER) represented by the vertical axisas a function of OSC as the horizontal axis;

FIG. 5 illustrates the basic concept of OSC optimization using thestrong writer with TPTP trace 3000 and the weak writer without TPTPtrace 3020 from FIG. 4;

FIG. 6A illustrates a detail flowchart of operation 2072 of FIG. 3Cfurther regarding the writer communicating with the radial zonecollection members, finding the Minimum OSC 2922;

FIG. 6B illustrates a detail flowchart of operation 2082 of FIG. 3Cfurther regarding the writer communicating with the radial zonecollection members, finding the Maximum OSC 2926;

FIG. 6C illustrates a detail flowchart of operation 2112 of FIG. 6Afurther successively decreasing the OSC value, and operation 2132 ofFIG. 6B further performs successively increasing the OSC value;

FIG. 7A illustrates a detail flowchart of operation 2022 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection 2910 members, optimizing the Minimum OSC 2922 to meet the ATWcriteria;

FIG. 7B illustrates a detail flowchart of operation 2032 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection members, the step optimizing the Minimum OSC 2922 to meet theWII criteria;

FIG. 8 illustrates the basic concept of optimizing the Minimum OSC 2902to meet the ATW criteria of operation 2022 of FIGS. 3B and 7A;

FIG. 9 illustrates the basic concept of optimizing the Minimum OSC 2902to meet the WII criteria of operation 2032 of FIGS. 3B and 7B;

FIG. 10A illustrates a detail flowchart of operation 2500 of FIG. 3Acontrolling a writer 222-224-200 within a disk drive 10 using writeparameter collection 2900 for at least write operations; and

FIG. 10B illustrates a detail flowchart of operation 2522 of FIG. 10Afurther using at least one of the Optimum OSC and the Maximum OSC.

DETAILED DESCRIPTION OF THE INVENTION

The invention optimizes the write performance of a writer within a diskdrive 10, including a read-write head 200 accessing a rotating disksurface 12, the coupled preamplifier 224, and the channel interface 222coupled to the preamplifier 224 as illustrated in FIG. 3A.

The invention includes a testing method 2000 illustrated in FIGS. 3A–3B.The testing method is applied to at least one writer in a disk driveduring the self-test phase to generate write parameters 2900, focused onthe Over Shoot Control (OSC) of the write current parameter whichimproves the reliability of write operations by that writer. The OSCparameter is involved in at least the operation of the preamplifier 224.

The inventors discovered that the OSC should be controlled based uponthe write field strength of the specific writer within the disk drive.Different writers within the same disk drive often possess distinctwrite field strengths, requiring distinct OSC settings during normaloperation. The inventors found that low temperature conditions againneed distinct OSC settings based upon the write field strength of thewriter.

In the following figures are flowcharts of at least one method of theinvention possessing arrows with reference numbers. These arrows willsignify flow of control and sometimes data supporting implementations,including at least one program step, or program thread, executing upon acomputer, inferential links in an inferential engine, state transitionsin a finite state machine, and dominant learned responses within aneural network. Arrows include references 2010, 2014, 2020, 2024, 2030,and 2034 in FIG. 3B; 2050, 2054, 2060, 2064, 2070, and 2074 in FIG. 3C;2110, 2114, 2120, and 2124 in FIG. 6A; 2130, 2134, 2150, and 2154 inFIG. 6B 2170, and 2174 in FIG. 6C; 2230, 2234, 2240, 2244, 2250, and2254 in FIG. 7A; 2270, 2274, 2280, 2284, 2290, and 2294 in FIG. 7B;2510, 2514, 2520, and 2524 in FIG. 10A; and 2550, 2554, 2560, and 2564in FIG. 10B.

The operation of starting a flowchart refers to at least one of thefollowing. Entering a subroutine in a macro instruction sequence in acomputer. Entering into a deeper node of an inferential graph. Directinga state transition in a finite state machine, possibly while pushing areturn state. And triggering a collection of neurons in a neuralnetwork.

The operation of termination in a flowchart refers to at least one ormore of the following. The completion of those operations, which mayresult in a subroutine return, traversal of a higher node in aninferential graph, popping of a previously stored state in a finitestate machine, return to dormancy of the firing neurons of the neuralnetwork. Termination will be denoted by the word “Exit” in the center ofan oval and includes the following references: 2016 in FIG. 3B; 2056 inFIG. 3C; 2116 in FIG. 6A; 2136 in FIG. 6B; 2176 in FIG. 6C; 2236 in FIG.7A; 2276 in FIG. 7B; 2516 in FIG. 10A; and 2556 in FIG. 10B.

A computer as used herein will include, but is not limited to aninstruction processor. The instruction processor includes at least oneinstruction processing element and at least one data processing element,each data processing element controlled by at least one instructionprocessing element.

The inventors adopted an approach based upon the premise that the OSCneeds to be reduced as much as possible for the least loss in Bit ErrorRate (BER), for the best use of the writer during the write operation.The inventors also explored a number of optimization schemes and foundthat constraining Minimum OSC 2922 to guarantee both an Adjacent TrackWrite (ATW) criteria, as well as guarantee a Write Induced Instability(WII) criteria, lead to significant reliability improvements.

FIG. 3A illustrates aspects of the invention as a refinement of FIG. 2C.

Two separate program systems are illustrated residing in Memory 1120.During self-test, after assembling disk drive 10, an initializationprogram 2000 generates at least one write parameter collection 2900.During regular operations, essentially after initialization, programsystem 3000, uses one or more write parameter collections 2900, 2930 toperform write operations. These write operations use the appropriatewriter to the tracks of the related radial zones using the OSCcollection 2920 members based upon estimates of the ambient temperatureof the disk surface 12 being accessed.

Note that memory 1120 may include both volatile and non-volatile memorycomponents. Initialization program system 3000 may preferably reside ina volatile memory component, essentially disappearing after self-testinitialization. Write parameter collections 2900, as well as programsystem 3000, preferably reside in one or more non-volatile memorycomponents, and are available whenever the system is powered up. Notethat during initialization process 2000, write parameter collection 2900may preferably reside in a volatile memory component, and eventually beinstalled in a non-volatile memory component toward the end ofinitialization.

The radial zones of the disk surface each include multiple tracks onthat disk surface with radial distances within that radial zone. A diskdrive may preferably have as many as 15 to 30 radial zones in manycontemporary applications.

The inventors found that a writer with a strong write field sufferssignificant reliability loss with high OSC due to increases in AdjacentTrack Write (ATW) errors, Track Per Inch (TPI) margins, Write InducedInstabilities (WII), read-write head degradation, and Head to DiskInterference (HDI) caused by Thermal Pole Tip Protrusion (TPTP). Theinventors found that a writer with a weak write field does not suffersignificant reliability loss with high OSC, opening the door to usinghigher OSC without the same problems as a strong writer.

Thermal Pole Tip Protrusion (TPTP) is caused by the materials in andaround the head slider expanding during write operations until part ofthose materials protrude, leading to contact with the rotating disksurface. Contact can degrade the write performance by altering theflying height. Contact can also wear down part of the disk surface.Taking into account TPTP gave the inventors significant insight intoboth read-write head degradation and Head to Disk Interference (HDI).The inventors have found that optimization of Overshoot Control (OSC),as disclosed herein, can minimize this problem to some extent.

FIG. 3B illustrates a detail flowchart of program system 2000 of FIG. 3Agenerating write parameters 2900 including an OverShoot Control (OSC)collection 2920 of FIG. 3A, regarding a writer communicating with themembers of a radial zone collection 2910.

Radial zone collection 2910 includes radially consecutive tracks onrotating disk surface 12 within disk drive 10.

The writer is contained within the disk drive 10. The writer iscomprised of a read-write head 200 communicating with a rotating disksurface 12, a preamplifier 224 coupled with the read-write head 200 anda channel interface 222 coupled with the preamplifier 224, within thedisk drive 10. The OSC collection 2920 includes an Optimum OSC 2924, aMinimum OSC 2922, and a Maximum OSC 2926.

Operation 2012 performs optimizing the OSC collection 2920 members tocreate a Bit Error Rate (BER). Operation 2022 performs optimizing theMinimum OSC 2922 to meet an Adjacent Track Writing (ATW) criteria basedupon the BER. Operation 2032 performs optimizing the Minimum OSC 2922 tomeet a Write Induced Instability (WII) criteria.

FIG. 3C illustrates a detail flowchart of operation 2012 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection 2910 members, optimizing the OSC Collection 2920 members tocreate the BER.

Operation 2052 performs generating a reference BER and a reference OSC,both based upon an initial channel value collection and an initial OSCvalue. Operation 2062 performs finding the Minimum OSC 2922 by testingbased upon the reference BER and the reference OSC value to create anOSC table 2990 containing at least two entries. Operation 2072 performsfinding the Maximum OSC 2926 by testing, based upon the reference BERand the reference OSC to update the OSC table 2990.

The initial channel value collection and initial OSC value maypreferably be generated as a result of performing one or both of thefollowing. Read channel optimizing for other parameters based upondefault values of the write current and of the OSC to create an initialRead Channel Optimization (RCO) parameter list, and read channeloptimizing to create an initial write current and the initial OSC basedupon the other initial RCO parameters. The initial OSC is based at leastpartially upon the default write current and the default OSC. Note thatthe RCO parameter list will include not only a write current (Wc), awrite OverShoot Control (OSC), but also a read bias (Read_(—)bias) andwrite bias (Write_(—)bias) as illustrated in FIGS. 2C and 3A.

Note that each of the OSC table 2990 entries contains an OSC value and aBER test value. The Optimum OSC 2924 is determined from the OSC table2990 to have a minimum BER test value, regarding the writercommunicating with tracks of the radial zone collection 2910.

FIG. 4 illustrates the effects of the Write Strength 2902 of variouswriters with and without the presence of Thermal Pole Tip Protrusion(TPTP), with the Bit Error Rate (BER) represented by the vertical axisas a function of OSC as the horizontal axis.

In FIG. 4, trace 3000 illustrates a very strong writer with the presenceof TPTP. The inventors found that the disk controller should use a lowerOSC when operating the writer in normal temperatures. The inventors alsofound that the disk controller should not use much higher OSC values forlow temperature operations.

In FIG. 4, trace 3010 illustrates a weak writer with the presence ofTPTP. The inventors found that the disk controller can use a lower OSCwhen operating the writer in normal temperatures with minimal BERincreases. The inventors also found that the disk controller should notuse higher OSC values for low temperature operations.

In FIG. 4, trace 3020 illustrates a very strong writer without thepresence of TPTP. The inventors found that the disk controller shoulduse a lower OSC when operating the writer in normal temperatures. Theinventors also found that the disk controller can use much higher OSCvalues for low temperature operations.

In FIG. 4, trace 3030 illustrates a weak writer without the presence ofTPTP. The inventors found that the writer can use a lower OSC whenoperating the writer in normal temperatures with minimal BER increases.The inventors also found that the writer needs higher OSC values for lowtemperature operations.

Determining at least three separate OSC parameters is preferred forwrite operation control of the writer. The Minimum OSC 2922 is preferredfor normal write temperatures. The Optimum OSC 2924 is preferred in afirst lower temperature range between essentially 15° Centigrade andessentially 5° Centigrade. The Maximum OSC 2926 is preferred below thefirst lower temperature range.

FIG. 5 illustrates the basic concept of OSC optimization using thestrong writer with TPTP trace 3000 and the weak writer without TPTPtrace 3020 from FIG. 4.

The inventors found that for a strong writer 3000, an optimum OSC 2924exists, often as the bottom of a bathtub shape, as illustrated by trace3000 of FIGS. 4 and 5. Too high an OSC value increases the Bit ErrorRate (BER), due to too strong a write field, or to Head DiskInterference (HDI) related issues. These problems occurred most oftennear the Outside Diameter tracks of the disk surface 12 communicatingwith the writer. The inventors also found that strong writers do notneed much of an increase in OSC for operating below normal temperatures.

The inventors found that for a weak writer 3020, there is a need forgreater OSC, particularly near the Outside Diameter tracks under normaltemperatures. The Bit Error Rate (BER) tends to saturate when using thehigher OSC range, particularly for most of the tracks from the MiddleDiameter to the Inside Diameter. Weak writers tend to need significantlyincreased OSC for low temperature operation.

In FIG. 5, for a strong writer 3000, the Minimum OSC 2922 and MaximumOSC 2926 are essentially within ΔBER multiplied by the minimum Bit ErrorRate (BER), which occurs using the Optimum OSC 2924. For a weak writer3020, the Minimum OSC 2952 is essentially within ΔBER multiplied by theminimum Bit Error Rate (BER), which occurs using the Optimum OSC 2954.Note that for the weak writer 3020, the Maximum OSC 2956 is essentiallythe same as the Optimum OSC 2954, both of which are at the maximumfeasible OSC. ΔBER is a fraction, preferably about 0.3.

These three members of the OSC collection 2920, regarding the strongwriter 3000 for a radial zone collection 2910 of tracks, are all smallerthan any of the OSC collection 2950 members regarding the weak writer3020 for a radial zone collection 2940.

FIG. 6A illustrates a detail flowchart of operation 2072 of FIG. 3Cfurther regarding the writer communicating with the radial zonecollection members, finding the Minimum OSC 2922.

Operation 2112 successively decreases an OSC value from the referenceOSC until a bit error rate test reports a BER for the OSC Value outsidea first bit error rate range based upon the reference BER. Operation2122 performs setting the Minimum OSC 2922 to the OSC value.

FIG. 6B illustrates a detail flowchart of operation 2082 of FIG. 3Cfurther regarding the writer communicating with the radial zonecollection members, finding the Maximum OSC 2926.

Operation 2132 performs successively increasing an OSC value from thereference OSC until a bit error rate test reports a BER for the OSCvalue outside a second bit error range based upon the reference BER.Operation 2142 performs setting the Maximum OSC 2926 to the OSC value.

The reference BER is preferably the minimum BER as illustrated in FIG.5. The first bit error range and second bit error range may be distinctranges, but preferably are within ΔBER multiplied by the reference BER.

FIG. 6C illustrates a detail flowchart of operation 2112 of FIG. 6Afurther successively decreasing the OSC value, and operation 2132 ofFIG. 6B further performs successively increasing the OSC value.

Operation 2172 performs saving the BER for at least one of the OSCvalues to the OSC table 2990.

The radial zone collection preferably includes a first track, tworadially neigboring tracks, and a radial neighborhood strip collectioncontaining the first track and the two radially neighboring tracks. Theradial neighborhood strip collection preferably includes at least twoadditional tracks belonging to the radial zone collection. The radialneighborhood collection preferably includes a total of 21 tracksradially neighboring the first track.

FIG. 7A illustrates a detail flowchart of operation 2022 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection 2910 members, optimizing the Minimum OSC 2922 to meet the ATWcriteria.

Operation 2232 performs setting an OSC value to the Minimum OSC 2922.Operation 2242 successively decreases the OSC value, whenever anAdjacent Track Write (ATW) test using the OSC Value provides a BER, forat least one of the radial neighborhood strip collection members,outside the ATW criteria based upon the reference BER. Operation 2252performs setting the Minimum OSC 2922 to the OSC value.

FIG. 7B illustrates a detail flowchart of operation 2032 of FIG. 3Bfurther regarding the writer communicating with the radial zonecollection members, the step optimizing the Minimum OSC 2922 to meet theWII criteria.

Operation 2272 performs setting an OSC value to the Minimum OSC 2922.Operation 2282 successively decreases the OSC value whenever measuringan Automatic Gain Control (AGC) range and an AGC average, based uponrepeated writing using the OSC value of a track belonging to the radialzone collection, indicates the AGC range exceeding a fraction of the AGCaverage. Operation 2292 performs setting the Minimum OSC 2922 to the OSCvalue.

FIG. 8 illustrates the basic concept of optimizing the Minimum OSC 2902to meet the ATW criteria of operation 2022 of FIGS. 3B and 7A.

The horizontal axis of FIG. 8 represents a write current setting of 40.2mA, and OSC settings from 0 to 28. The vertical axis on the leftrepresents the logarithm base 10 of the Bit Error Rate (BER). Thevertical axis on the right Channel Statistical measurements (CSM) from 0to 4000.

In FIG. 8, traces from 3070 and above represent the adjacent track biterror rates measured after repeated writing of the adjacent tracks tothe test track by operation 2292. The trace 3072 represents the BERcurve for a strong writer. The traces below 3072 represent the CSMvalues measured for the corresponding BER traces 3070 and above.

FIG. 8 indicates the experimental findings of the inventors regardingadjacent track writing errors and the relationship of Write Current Wcand OverShoot Control OSC based upon the strength of a writer. Thehigher the write strength of a writer, the greater the increasedadjacent track writing noise from increased OSC. The increased adjacenttrack writing noise can be seen as increase in the log of BER.

The inventors concluded, as illustrated in FIG. 8, that the Minimum OSC2922 should guarantee an ATW criteria, which is preferably 10^1.5multiplied by the BER loss after a repetition of preferably 200 timeswriting both adjacent tracks. The inventors found that if the ATWcriteria is not satisfied, the Minimum OSC 2922 should be decreased, andthe ATW test performed again, until the ATW criteria is met.

FIG. 9 illustrates the basic concept of optimizing the Minimum OSC 2902to meet the WII criteria of operation 2032 of FIGS. 3B and 7B.

In FIG. 9, the vertical axis represents the percentage of Automatic GainControl (AGC) range to AGC averages found at the preamplifier 224. Thehorizontal axis represents the combination of Write Current (Wc) as thelower number and OverShoot Control (OSC) as the higher number in labelstrip at the bottom of the Figure.

The inventors relied upon experimental data, which FIG. 9 summarizes, toconclude the following. Higher write strength causes greater WriteInduced Interference (WII). Measuring Automatic Gain Control (AGC)changes after write operations provide a good indication of WII. TheMinimum OSC 2922 should guarantee a WII criteria during repeated trackwritings. If the Minimum OSC 2922 does not guarantee the WII criteria,it should be reduced, and the test repeated.

The WII criteria should preferably be the AGC variation within a fixedratio of the average AGC. One preferred fixed ratio is about tenpercent. The repeated track writing should preferably be at least fiftyrepetitions.

The inventors have found the test method should preferably be applied toat least four radial zones of the disk surface accessed by the writer.The inventors have found the test method should preferably interpolatethe OSC Collection for all of the radial zone collections, based upontested OSC Collections regarding the writer for each of the testedradial zone collection members. It is preferable to perform read channeloptimizing based upon these generated write parameter collections 2900.

The write parameter collection 2900 is a product of the processillustrated as operation 2000 of FIGS. 3A–3B.

The process of making a disk drive 10 may preferably include thefollowing. Performing the steps of method 2000 of FIGS. 3A–3B to createthe write parameter collection 2900, regarding the writer 2902 for atleast one of the radial zone collections 2910. And installing writeparameter collection 2900 into embedded controller 1000 within the diskdrive 10. Note that installation preferably includes writing writeparameter collection 2900 into a non-volatile memory component of memory1120. Disk drive 10 is a product of this process.

The program system 2000 illustrated in FIGS. 3A–3B is an implementationof the method 2000 generating the write parameter collection 2900 ofFIG. 3A. The apparatus implementing this method 2000 generating thewrite parameter collection 2900 includes a means for each of theoperations shown in FIG. 3B. These means may include program steps, aswell as, finite state machines, implementing at least part of eachoperation and the writer.

The invention also includes a method 2500 of controlling a writer222-224-200 within a disk drive 10 using an OverShoot Control (OSC)Collection 2920 regarding the writer for a radial zone collection 2910including at least two tracks on the rotating disk surface 12 asillustrated in FIG. 3A.

FIG. 10A illustrates a detail flowchart of operation 2500 of FIG. 3Acontrolling a writer 222-224-200 within a disk drive 10 using writeparameter collection 2900 for at least write operations.

Operation 2512 performs using the Minimum OSC 2922 for write operationsby the writer within the radial zone collection 2910 whenever operatingwithin a normal temperature range. Operation 2522 performs using atleast one of the Optimum OSC 2924 and the Maximum OSC 2926 for writeoperations by the writer within the radial zone collection 2910 wheneveroperating below the normal temperature range.

FIG. 10B illustrates a detail flowchart of operation 2522 of FIG. 10Afurther using at least one of the Optimum OSC and the Maximum OSC.

Operation 2552 performs using the Optimum OSC 2924 for write operationsby the writer within the radial zone collection 2910 whenever operatingin a first lower temperature range. Operation 2562 performs using theMaximum OSC 2926 for write operations by the writer within the radialzone collection 2910 whenever operating below the first lowertemperature range.

The preceding embodiments have been provided by way of example and arenot meant to constrain the scope of the following claims.

1. A method generating an OverShoot Control (OSC) collection regarding awriter for members of a radial zone collection including at least threeradially consecutive tracks on a rotating disk surface within a diskdrive, wherein said writer is contained within said disk drive, whereinsaid writer is comprised of a read-write head communicating with arotating disk surface, a preamplifier coupled with said read-write headand a channel interface coupled with said preamplifier, within said diskdrive wherein the members of said OSC collection include an Optimum OSC,a Minimum OSC and a Maximum OSC, wherein said method is comprised,regarding said writer communicating with said radial zone collectionmembers, of the steps of: optimizing said OSC collection members tocreate a Bit Error Rate (BER); optimizing said Minimum OSC to meet anAdjacent Track Writing (ATW) criteria based upon said BER; andoptimizing said Minimum OSC to meet a Write Induced Instability (WII)criteria.
 2. The method of claim 1, wherein, regarding said writercommunicating with said radial zone collection members, the stepoptimizing said OSC Collection members to create said BER, is furthercomprised of the steps of: generating a reference BER and a referenceOSC, both based upon an initial channel value collection and an initialOSC value; finding said Minimum OSC by testing based upon said referenceBER and said reference OSC value to create an OSC table containing atleast two entries; and finding said Maximum OSC by testing based uponsaid reference BER and said reference OSC to update said OSC table;wherein each of said OSC table entries contains an OSC value and a BERtest value; and wherein said Optimum OSC is determined from said OSCtable to have a minimum BER test value.
 3. The method of claim 2,wherein, regarding said writer communicating with said radial zonecollection members, the step finding said Minimum OSC, is furthercomprised of the steps of: successively decreasing an OSC value fromsaid reference OSC until a bit error rate test reports a BER for saidOSC Value outside a first bit error rate range based upon said referenceBER; and setting said Minimum OSC to said OSC value; wherein the stepsuccessively decreasing said OSC value is further comprised of the stepsof saving said BER for at least one of said OSC values to said OSCtable.
 4. The method of claim 2, wherein, regarding said writercommunicating with said radial zone collection members, the step findingsaid Maximum OSC, is further comprised of the steps of: successivelyincreasing an OSC value from said reference OSC until a bit error ratetest reports a BER for said OSC value outside a second bit error rangebased upon said reference BER; setting said Maximum OSC to said OSCvalue; wherein the step successively increasing said OSC value isfurther comprised of the steps of saving said BER for at least one ofsaid OSC values to said OSC table.
 5. The method of claim 1, whereinsaid radial zone collection members include a first track, two radiallyneigboring tracks, and the members of a radial neighborhood stripcollection include said first track and said two radially neighboringtracks; wherein, regarding said writer communicating with said radialzone collection members, the step optimizing said Minimum OSC to meetsaid ATW criteria, is further comprised of the steps of: setting an OSCvalue to said Minimum OSC; successively decreasing said OSC valuewhenever an Adjacent Track Write test using said OSC Value provides aBER for at least one of said radial neighborhood strip collectionmembers outside said ATW criteria based upon said reference BER; andsetting said Minimum OSC to said OSC value.
 6. The method of claim 5,wherein the step successively decreasing said OSC value whenever saidAdjacent Track Write test is further comprised of the steps of:repeatedly writing said radially neighboring tracks using said OSCvalue; performing said Adjacent Track Write test using said OSC Valueproviding said BER for each of said radial neighborhood strip collectionmembers until said BER is outside said ATW criteria based upon saidreference BER until said BER is outside said ATW criteria based uponsaid reference BER for said radial collection member; decreasing saidOSC value whenever said BER is outside said ATW criteria based upon saidreference BER; and repeating the previous steps whenever said BER isoutside said ATW criteria based upon said reference BER for at least oneof said radial collection members.
 7. The method of claim 1, wherein,regarding said writer communicating with said radial zone collectionmembers, the step optimizing said Minimum OSC to meet said WII criteria,is further comprised of the steps of: setting an OSC value to saidMinimum OSC; successively decreasing said OSC value whenever measuringan Automatic Gain Control (AGC) range and an AGC average, based uponrepeated writing using said OSC value of a track belonging to saidradial zone collection, indicates said AGC range exceeding a fraction ofsaid AGC average; and setting said Minimum OSC to said OSC value.
 8. Themethod of claim 7, wherein the step successively decreasing said OSCvalue whenever measuring is further comprised of the steps of:repeatedly writing said track using said OSC value to obtain said AGCaverage, an AGC minimum and an AGC maximum; and setting said AGC rangeto said AGC maximum minus said AGC minimum.
 9. A method of generating anOverShoot Control (OSC) collection regarding said writer for all of saidradial zone collections on said rotating disk surface within said diskdrive of claim 1, comprising the steps of: for each member of a testzone collection comprising at least four of said radial zonecollections, performing the steps of claim 1 regarding said writer; andinterpolating said OSC Collection regarding said writer for all of saidradial zone collections based upon said OSC Collections regarding saidwriter for each of said test zone collection members.
 10. A method ofread channel optimization regarding said writer of claim 9, comprisingthe steps of: performing the steps of claim 9; and wherein said method,for each of said radial zone collections, is further comprised of thestep of: read channel optimizing based upon said Minimum OSC regardingsaid writer for said radial zone collection to create members of a writeparameter collection, regarding said writer and for said radial zonecollection, including said OSC collection members regarding said writerand for said radial zone collection.
 11. The method of claim 10, furthercomprising at least one member of the collection comprising the stepsof: read channel optimizing for other parameters based upon a defaultwrite current and a default of said OSC to create an initial ReadChannel Optimization (RCO) other parameter list; and read channeloptimizing to create an initial write current and said initial OSC basedupon said initial RCO other parameters; wherein said initial OSC isbased at least partially upon said default write current and saiddefault OSC.
 12. A method of making said disk drive of claim 10,comprising the steps of: performing the steps of claim 10 to create saidwrite parameter collection, regarding said writer for at least one ofsaid radial zone collections; and installing said write parametercollection into an embedded controller within said disk drive.
 13. Thedisk drive as a product of the process of claim
 12. 14. The method ofclaim 12, wherein the step performing the steps of claim 10, is furthercomprised of at least one member of the collection comprising the stepsof: performing the steps of claim 10 to create said write parametercollection, regarding said writer for all of said radial zonecollections; and performing the steps of claim 10 to create said writeparameter collection, regarding a second of said writers included insaid disk drive for at least one of said radial zone collections on asecond rotating disk surface communicating with said read-write headincluded in said second writer; for each of at least three of saidwriters, included in said disk drive, communicating with a correspondingdisk surface, performing the steps of claim 10 to create said writeparameter collection, regarding said writers for at least one of saidradial zone collections on said corresponding rotating disk surface; andfor each of said writers, included in said disk drive, performing thesteps of claim 10 to create said write parameter collection, regardingsaid writers for all of said radial zone collections on saidcorresponding rotating disk surface.
 15. A method of controlling awriter within a disk drive, wherein said writer is comprised of achannel interface coupled with a preamplifier, in turn coupled with aread-write head communicating with a rotating disk surface within saiddisk drive, wherein said disk drive contains an OverShoot Control (OSC)Collection regarding said writer for a radial zone collection includingat least two tracks on said rotating disk surface, wherein said OSCcollection includes an Optimum OSC, a Minimum OSC and a Maximum OSC,wherein a radial zone collection is comprised of at least three radiallyconsecutive tracks on said rotating disk surface, wherein said method iscomprised the steps of: using said Minimum OSC for write operations bysaid writer within said radial zone collection whenever operating withina normal temperature range; and using at least one of said Optimum OSCand said Maximum OSC for write operations by said writer within saidradial zone collection whenever operating below said normal temperaturerange.
 16. The method of claim 15, wherein the step using at least oneof said Optimum OSC and said Maximum OSC is comprised of at least onemember of the collection comprising the steps of: using said Optimum OSCfor write operations by said writer within said radial zone collectionwhenever operating in a first lower temperature range; and using saidMaximum OSC for write operations by said writer within said radial zonecollection whenever operating below said first lower temperature range.17. The method of claim 16, wherein said first lower temperature rangeis between approximately 15° Centigrade and approximately 5° Centigrade.18. The method of claim 15, wherein said rotating disk surface includesat least two of said radial zone collections, each of said radial zonecollections includes at least three radially consecutive tracks on saidrotating disk surface; wherein said method is further comprised, foreach of at least two of said radial zone collections, of the steps of:using said Minimum OSC for write operations by said writer within saidradial zone collection whenever operating within a normal temperaturerange; and using at least one of said Optimum OSC and said Maximum OSCfor write operations by said writer within said radial zone collectionwhenever operating below said normal temperature range.
 19. The methodof claim 15, wherein said disk drive includes at least two of saidwriters, each of said writers comprised of a channel interface coupledwith a preamplifier, in turn coupled with a read-write headcommunicating with a rotating disk surface within said disk drive;wherein, for each of at least two of said writers, said disk drivecontains an OverShoot Control (OSC) Collection regarding said writer fora radial zone collection including at least three radially consecutivetracks on said rotating disk surface; wherein said method is furthercomprised, for each of at least two of said writers, of the steps of:using said Minimum OSC for write operations by said writer within saidradial zone collection whenever operating within a normal temperaturerange; and using at least one of said Optimum OSC and said Maximum OSCfor write operations by said writer within said radial zone collectionwhenever operating below said normal temperature range.
 20. The methodof claim 19, wherein said method is further comprised, for each of saidwriters, of the steps of: using said Minimum OSC for write operations bysaid writer within said radial zone collection whenever operating withina normal temperature range; and using at least one of said Optimum OSCand said Maximum OSC for write operations by said writer within saidradial zone collection whenever operating below said normal temperaturerange.